After much investigation, I have finally found whats been causing headaches with the datto. Almost since I got the car, it has had some minor issues with idling. After giving the car some stick, it has tended to idle higher afterwards. I took the car to Shaun @ Allstar some time ago, and he said it could be the throttlebody pin bent, so the butterfly wasn't closing properly. This seemd like the problem, and the insitu solution was to just back of the idle control bolt when the idle rose. A consequence of the idling has been the trans temperature rising, and the engine temperature rises if the car is stopped as its trying to pull away. Frustrating! And also, after the tune up, the car wasn't regulating boost at higher levels. So at around 20psi, there was boost fluctuations of around +- 3psi.

After my first pass down the drags on Monday, the car came back the return road idling at 4,500rpm!!!! I pulled of the front intercooler piping to find the T/B was fine and the butterfly was closing beautiful.....So - where was the air coming from?

Answer:
INLET MANIFOLD!

After getting the car back to the workshop, I discovered some rather decent sized cracks had developed in several places on the inlet manifold. So:
a. This has been the cul[rit of idle problems;
b. This has been causing slightly higher temps in trans and engine;
c. This has been causing boost fluctutations.

So now, i'm pulling the manifold off to get repaired. I am EXTREMELY happy, as ive finally found the cause of some niggling problems! So people, if your seeing these symptoms - check the inlet manny!!!! Very, very relieved to have found the cause. They weren't serious issues, but frustrating!

Thankyou all.

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1972 Datsun 1600 SR20det - 330hp @ 18psi, 461Nm Torque
1934 Ford Coupe - S/C BB Chev

Hi, the first thing i was going to say was that it sounds like an air leak somewhere - glad you found out exactly where it was coming through tho...

Hopefully that hasn't been leaning it out too mash as cracks in the manifold are after the airflow meter, so no compensation from the computer

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Happiness is watching the race.... in your rearview mirror

Shouldn't be a problem, because if anything the car loses boost through the cracks. So it probably runs abit richer at the higher boost levels. It may be running slightly lean through idle - but nothing too serious. IM getting it checked out next week hopefully. But it sounds fine, and as it was the AFR's were tuned very, very safe. Anyhow, if all goes well I may get a tune for C16 and more booooooost.

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1972 Datsun 1600 SR20det - 330hp @ 18psi, 461Nm Torque
1934 Ford Coupe - S/C BB Chev